More screen experimentation...

[ContraMoto]

Experimentation can be expensive and time-consuming. Yesterday evening and this morning I taped up a Laminar Lip onto my Scout screen at 5 different heights, along with changing the height of my head up and down (using some foam pads on the seat). Each change took an hour, including a ride out to the freeway, riding up and back a few exits, changing the sitting height.... My test priorities were (in order of importance): (1) buffeting: trying to eliminate it completely; and (2) sound levels: Quieter is better, but is secondary to "no buffeting." Final priority was to have the screen top as low as possible.

Since I hate buffeting so much, I am fine-tuned to it and trust my subjective judgement. The "standard" is naked-bike...it might be windy and loud, but there's no buffeting. Can I relieve the wind pressure, achieve some quiet, and still have naked-bike lack of buffeting?

As for testing for wind noise...I have helmet speakers in my Qwest (SMH10), and I played the same song at the same volume setting on every run. As a benchmark, I can't hear the song at that volume at all on a naked bike at 75mph.

After all those runs...in the final configuration I can see the road merely 20' in front of the bike. The screen is lower than I would have ever guessed. The Laminar Lip is only 1/4" above the top of the screen.

I got it right, and the result is just remarkable. I can hear the music loud and clear. The motor and surrounding traffic is louder than the wind. I even placed a cell phone call home and my wife said it sounded barely louder than calling from the car. With foam earplugs in, it is almost spooky quiet. I merely turn the volume of the speakers up a little and I can still hear the tunes. The best part...I feel NO buffeting at all. What would stop me from going on longer adventures would be head-buffeting. It just takes all the joy out of riding for me, and I just had to get rid of it.

I am so stinkin' pleased with the result I have to pinch myself. I get plenty of wind on arms and legs and I get to drive a bike without an acre of plastic all over it. When I was searching for a bike, I kept standing between a touring bike and a naked bike. I jokingly asked the BMW salesman if they could cut the lower fairings off an RT for me, and give me the bike with just the top half. The R1200ST was tempting, but I was ultimately turned off by the plastic tank and angular front end.

The R1200R is among the last bikes made in the classic design (other than some Harley models and the Bonneville line, I can't think of any others). For me, the Scout fairing makes the bike perfect for what I want to do.

[Anyname]

So provide the specifics for the magic formula: What height shield? What seat? How tall and what's your inseam? Pictures with the laminar lip installed?

[ka5ysy]

Post photos please....

[ContraMoto]

Here's my take on screens, reached after spending far too many hours experimenting, riding, fabricating and reading. I've also visited with Mark from CalSci and Paige from Aeroflow. BTW -- Paige understands windflow on a motorcycle on a surprisingly subtle level. Very thoughtful guy; an artist by trade/training and a tinkerer by nature.

Inseam, seat height, etc...do not matter one iota. All that matters is: Where is your head when you're sitting on the bike the way you want to sit? You must first figure out your legs, feet, hands, rear end...because if that's not right you're not going to be comfortable anyway. Do not tinker with your riding position in the interest of wind protection.

Then, you have to make a choice. Do you want the screen really low, or really high.

Low = smooth air at your head, but lots of it and straight at you. If the screen is low enough, you can eliminate buffeting. In my own view...buffeting is priority No. 1. I cannot ride a bike with my head as a high-frequency punching bag.

High = you can get the air flow off your upper torso and head, but it can "tumble" over the top of the screen and buffet you. Holes in the lower part of the screen make NO difference on a tall screen. Those holes only make a difference if they lead to a "chute" that sends air UP the back of the screen. See the design of BMW's touring bike screens, the Aeroflow and the Parabellum scout.

Medium screen = throws air right in the base of your helmet. It's hecka loud, and buffets you to pieces. No good.

This why so many people report best success after they've cut their short/medium screens down low. You get it low enough and the turbulent air stays below your neck. Smooth air at the head can be managed with earplugs. Success...if you are OK with the high-speed wind at your head. I am...for short rides. But, I want to do long trips and I wanted softer air at the helmet.

Now to the question of measurement parameters. In my experience, higher and closer is better. By a simple fact of geometry, they can go hand in hand. By tilting the screen back, the top of it moves closer. That allows it to be taller while still looking over it (I like the rule of the Laminar Lip folks: You need to see the road at 40' or closer).

My screen top is level with my bottom lip, and 15" away. In practical terms, that means the top edge is about even with the switchgear on the handlebars. So, it doesn't matter what my inseam is or seat height -- what matters is where the top of the screen is in relation to my head. Anybody trying to duplicate anyone else's setup should only be concerned with where the screen top is in relation to their own head. Find that point in space, and work down to the mounting bracket from there when choosing an actual screen dimension.

I added a Laminar Lip to my screen, but it's a luxury. The screen works great, but the Lip makes the air at the helmet just that little bit softer. Since the Lip goes on or off the bike as needed, I'll just put it on if I'm going on a long ride. I don't have a pic of the Lip since I only rode it duct-taped on the bike to experiment. I'm not mounting it until I get my new seat and can cut the Scout shield down to its final size (I'm moving from tall to standard seat height and will trim the shield accordingly).

Final notes -- my setup is working so well because I have a fairing in front of the tank chunnels. Riders using only screens will have to live with the turbulence that comes from there. There is no cure for that that I am aware of, besides a Scout or similar fairing.

But I think the key in any event is: Either keep the screen short (2" or so above the instruments) or tilt it back and go as high as you can and still see the road 40' in front of the bike. In between just seems to give people fits, not only on our bikes but on all models of bikes.

[deilenberger]

ContraMoto,

I generally agree - but suggest the use of inseam, height, seat-height (and probably arm length) allows people to judge about where their head will end up in relation to the screen top. It might be possible to determine the head position relative to the screen top if another person was available to measure it, but trying to DIY with one person, it's Orcum Razor - doing the measurement changes the position.

I definately agree that holes in the lower portion of the screen do little good.. when working with Mark Lawrence on the CalSCI screen, he had me changing size of the holes to see what the effect would be. I ended up with quite large holes in the screen, that I then closed up using masking tape. There was very little effect on the buffeting I experienced.

I think one thing you missed is the angle of the screen also has another effect - the "tumbling" off the top of the screen is reduced when the screen is tilted back.

As an extreme example - consider a perfectly vertical piece of plastic in a 50 MPH wind. Air is going to be sucked into the vacuum formed behind the screen and collapse, this is the cause of buffeting. Then consider the same piece of plastic in a horizontal plane - there will be no real resistance to the airflow - and no collapse of the airstream behind the plastic. The DonC block achieves this. As a side effect, it also decreases the height. I have a modified BMW touring mount that achieves the same thing as Don's blocks do (the bottom loop was extended about 1.25").. and the small Cee-Bailey that caused turbulent airflow and the large Cee-Bailey that caused turbulent airflow DO NOT when tilted back with the modified mount.

It isn't just height - it's also the angle of attack of the screen to the airflow. I had the same experience with the CalSci - unbearable turbulence at the stock touring mount angle, almost no turbulence when used with the modified mount. Mark had originally thought that more upright (less angle) would help, so using spacers he provided, we tried tilting the screen more upright (spacers under the top mount points.) It made things MUCH worse. Putting the same spacers under the bottom mounts - turbulence became much less of an issue. I believe Mark now suggests the use of DonC spacer if turbulence is a problem.

Great discourse.. and aside from my quibbles above - dead on.

[dbrick]

Don's right, except about Ockham's Razor, which postulates that the simpler solution is usually correct. He's thinking of Heisenberg's Uncertainly Principle.

[angellr]

Don's right, except about Ockham's Razor, which postulates that the simpler solution is usually correct. He's thinking of Heisenberg's Uncertainly Principle.

Here is a link to Occam's [Ockham] Razor http://en.wikipedia.org/wiki/Occam's_razor

Believe you are right ... it is the HUP - http://en.wikipedia.org/wiki/Uncertainty_principle

[2wheels]

And another thing - why do raindrops get blown down my visor(rarely since rain stops play!)whereas bugs get blown over the top?

Also, what effect does air temperature and humidity have on aerodynamics? On a ride to-day there seemed to be more wind noise on my outward journey, but less on return when temperature had dropped about 5C.

[ContraMoto]

I think one thing you missed is the angle of the screen also has another effect - the "tumbling" off the top of the screen is reduced when the screen is tilted back.

Yes, I quite agree. The screen needs to be at least flatter than the fork rake, and the flatter the better. The double benefit of flatter -- it can be closer to the head, and taller!

[dbrick]

And another thing - why do raindrops get blown down my visor whereas bugs get blown over the top?

I have no idea, but have wondered the same. And how the heck do the drops get onto the inside of the lenses of my eyeglasses?

Also, what effect does air temperature and humidity have on aerodynamics? On a ride to-day there seemed to be more wind noise on my outward journey, but less on return when temperature had dropped about 5C.

I bet there was some wind blowing either with or against you, just enough so that there was an audible difference between the greater noise created by (bike speed + wind velocity) compared to the lesser noise created by (bike speed - wind velocity).

[ContraMoto]

And another thing - why do raindrops get blown down my visor(rarely since rain stops play!)whereas bugs get blown over the top?

Also, what effect does air temperature and humidity have on aerodynamics? On a ride to-day there seemed to be more wind noise on my outward journey, but less on return when temperature had dropped about 5C.

Hmmm...just speculatin'...

I ride the same stretch of freeway out and back all the time. It's where I do my test runs, plus it's the way outta town toward the coast. On every outbound run, I initially think I'm getting more noise/buffeting than I expect. Then I turn around and it's smoother coming back. It's the prevailing wind...going out, I'm headed toward the hills over which the wind blows. It's messy air. Coming back, it's less of a nuisance. So...you could just be experiencing an environmental difference.

Other than that...some aerodynamic principles: Colder air is denser, and increases the force on whatever it blows onto. But...it's only a little less dense. Hard to believe you could perceive the difference given all that's happening on a windy motorbike.

Wind resistance (force) increases with the square of speed, so things can get really tough, really fast, once you're moving along.

And, contrary to popular lore, humid air is less dense and lighter, and offers less wind resistance. I cringe when I hear baseball and golf announcers talk about how "the ball isn't carrying as far because it's humid." The opposite is true!

[Peter1200r]

My experience:

I am 5' 11.5 inches with a 31 inch inseam, and I sit (on my 09 R1200R) on a standard seat pan that has been custom re-covered by Rick Mayer. As of recently, I have 2 screens in addition to my stock sport screen - the largest (XL) Cal Sci and the largest (26") Cee Bailey. I use the Don C tilt block.

The Cal Sci gives me no helmet buffeting at 110 km/h (the speed limit in my part of Australia), and a little wind noise from the top of my helmet that disappears if I hunker down by about 1".

The Cee Bailey eliminates the wind noise at the top of the helmet, and gives no helmet buffeting. The top of the screen is about level with my mouth. I haven't swapped back and forth between the two screens yet, but having ridden maybe 2000 km with the Cal Sci before installing the Cee Bailey and then riding a further 1500 km, my feeling is that things are quieter with the Cee Bailey, but with a little more lower torso buffeting than I noticed with the Cal Sci.

In the rain with the Cee Bailey I get occasional raindrops swirling up past my chin to the inside of my visor (Shoei RF1100). I did not notice this with the Cal Sci, with which I also experienced heavy rain.

With both screens I can feel helmet buffeting if I lean back about 6" or more behind my normal comfortable riding position.

So, both are pretty good, and I haven't decided which is better for me. I suspect both are very close to the best possible outcome for me on this bike.

Peter

[redwing]

My bike has a sport shield and my head is completely in air .... I feel pressure at about mid chest. I ride in little or no traffic. IMHO.... I get buffeting at 100 feet behind a semi. The worst buffeting came from a pickup pulling a trailer with 4 or 5 four wheel ATVs. It was terrible. Every 3 or 4 seconds my head was being pushed left or right. In testing different shields with different heights is the traffic thick?

Robert

[ContraMoto]

In testing different shields with different heights is the traffic thick?

Robert

Traffic makes the air bumpy, no doubt. I test on the freeway since I can ride 80mph safely, but it's always messy air. To and from the freeway I ride on empty backroads and can ride 50-60mph. MUCH smoother.

[nylife]

today was my first screen experimentation, so here it goes:

when i bought the bike it came with a standard BMW touring screen and it really was not bad upto about 80 sometimes less depending on the wind conditions outside, then i purchased DON.C block and thing got a little smoother if i can call the wind hitting me smoother hope that makes sense.
Next step was to try to achieve a little more wind protection for the colder month, so i figured i will start experimenting now and purchase a 17inch(according to the seller) C/B shield, it was installed today my observations are that it takes the presure of my chest but now the wind hits me right on the helmet and while i do not have any buffeting the wind noise has increased.
another observation as it was already stated in this thread it depended which way i was going, riding south today on the Garden State Pkway was much smoother, then when i was riding back North.
Next step is probably to try the 20inch screen and see if the wind will go over the top of the helmet.

oh last but not least i am 5'8 with 30 inseam, i have standard seat(which sucks lol), i have 1inch risers.

I saw in another thread a post by deilenberger offering to test ride some of his screens, i dont think i live that far from him and may have to take him up on that offer to properly determine what size would work best.

[ErikM]

I'll just add that in my experience the "inseam spec" is pretty much irrelevant since I can have a 30" inseam and be 6' tall, someone else can have a 30"inseam and be 5'10", thses two riders would have different screen hight requirements. The spec that really matters is from the waist up, or how high up is ones head in relation to air flow..

[deilenberger]

I'll just add that in my experience the "inseam spec" is pretty much irrelevant since I can have a 30" inseam and be 6' tall, someone else can have a 30"inseam and be 5'10", thses two riders would have different screen hight requirements. The spec that really matters is from the waist up, or how high up is ones head in relation to air flow..

Erik,

We generally include both height AND inseam - to help people determine torso height. Or "the waist up" height.

[deilenberger]

I saw in another thread a post by deilenberger offering to test ride some of his screens, i dont think i live that far from him and may have to take him up on that offer to properly determine what size would work best.

Well, if you can get here this weekend, I'll be around.. but if not - I will be driving (grrr..) coast-2-coast-2-coast for 5 weeks, so the end of August would be the next opportunity. I'm off Exit 98..

[nylife]

I saw in another thread a post by deilenberger offering to test ride some of his screens, i dont think i live that far from him and may have to take him up on that offer to properly determine what size would work best.

Well, if you can get here this weekend, I'll be around.. but if not - I will be driving (grrr..) coast-2-coast-2-coast for 5 weeks, so the end of August would be the next opportunity. I'm off Exit 98..

this weekend all i got left in terms of time is monday, but this is in no way a rush i can wait till august so if anything have a safe ride

[nylife]

today was my first screen experimentation, so here it goes:

when i bought the bike it came with a standard BMW touring screen and it really was not bad upto about 80 sometimes less depending on the wind conditions outside, then i purchased DON.C block and thing got a little smoother if i can call the wind hitting me smoother hope that makes sense.
Next step was to try to achieve a little more wind protection for the colder month, so i figured i will start experimenting now and purchase a 17inch(according to the seller) C/B shield, it was installed today my observations are that it takes the presure of my chest but now the wind hits me right on the helmet and while i do not have any buffeting the wind noise has increased.
another observation as it was already stated in this thread it depended which way i was going, riding south today on the Garden State Pkway was much smoother, then when i was riding back North.
Next step is probably to try the 20inch screen and see if the wind will go over the top of the helmet.

oh last but not least i am 5'8 with 30 inseam, i have standard seat(which sucks lol), i have 1inch risers.

I saw in another thread a post by deilenberger offering to test ride some of his screens, i dont think i live that far from him and may have to take him up on that offer to properly determine what size would work best.

Phase 2:
I bought another screen from the board member this time i got large(22inch) calsci and in short its pretty much perfect, i get enough air around me not to feel hot, today was 90+ and it was perfectly fine and i had zero buffeting and very little wind noise all the way up to 90mph. i think i am done with screen